Usually, an exhaust system of a combustion engine is equipped with devices for cleaning or re-treating the exhaust gases conducted away from the combustion engine. There it can be necessary to introduce a liquid educt into the exhaust gas flow, to evaporate it therein and intermix it with the exhaust gas. For example, it may be required to admix a fuel to the exhaust gas upstream of an oxidation catalytic converter in order to bring about a heating-up of the exhaust gas flow through an exothermic conversion of the fuel in the oxidation catalytic converter. The heated-up exhaust gas flow can then be utilized downstream of the oxidation catalytic converter for heating up a further exhaust gas treatment device to operating temperature or to regeneration temperature, for example another catalytic converter or a particle filter. Furthermore, SCR systems are known, which operate with selective catalytic reaction and are equipped with an SCR catalytic converter which absorbs NOx from the exhaust gas flow. Upstream of the SCR catalytic converter a suitable reaction agent is fed to the exhaust gas flow, for example ammonia or urea, preferentially a watery urea solution. In the SCR catalytic converter the ammonia then causes a conversion of the embedded nitric oxides into nitrogen and water.
With respect to all educts fed into the exhaust gas flow in liquid form it is true that the desired effect can be satisfactorily achieved only when between the introduction point of the liquid educt and a consumer location of the educt an adequate evaporation of the educt as well as an adequate mixing-through of the gaseous educt with the exhaust gas flow can take place. For this purpose, the mixing and/or evaporating devices mentioned at the outset are employed, which are arranged in the flow path of the exhaust gas between the introduction point of the educt and the consumption point of the educt.